Variable pitch screw propeller



March 6, 1934. E. LANzERoTTl-SPINA 1,950,117

VARIABLE PITCH SCREW PRIOPELLR y Fileduune so, 1952 4 snets-sheet 14 f fe March 6, 1934. E. LANzERoTTl-SPINA 1,950,117

VARIABLE PITCH VSCREW PROPEILLER Filed June 30, 1932 4 Sheets-Sheet 2 lr"ig.2. l

afa/reu March ai, i934.

E. LANzERoTTl-SPINA VARIABLE PITCH SCREW PROPELLER Filed June so. 1932 sheets-sheet 4 Patented Mar. 6, 1934 VARIABLE PITCH SCREW PROPELLER Ettore Lanzerotti-Spina, deceased, late of Prebend Gardens, Stamford Brook, London, England, by Amelia Ann Lanzerotti-Spina, executrix, London, England Application June 30, 1932, Serial No. 620,271

' In Great Britain July 7, 1931 7 Claims. (Cl. 17o-163) This invention relates to variable pitch propellers which employ for pitch adjustment a nonreversible or self-locking mechanism comprising a non-rotatable sliding sleeve co-axial with the propeller blade having both steep and shallow screw threads which engage with corresponding threads upon the root of the propeller blade and upon a rotatable sleeve respectively, the blade and sleeve being prevented from moving longitudinally.

In constructions of this kind heretofore devised the propeller blades have been driven, and the centrifugal forces upon them resisted, by cylindrical extensions of a hub on the propeller shaft, within which extensions the blade roots are received; though further support has been afforded by a spider or trunnioned sleeve, the arms or trunnions of which enter the blade roots. To these same hub extensions the non-rotatable sliding threaded sleeve has been splined, the threaded root of the blade lying within that sleeve andtthe threaded rotatable sleeve surroundmg 1 It is the purpose of the present invention to improve the construction of this class of variable pitch propeller with a view to reducing its weight, reducing the overhang of the propeller beyond the adjacent propeller shaft bearing, and reducing the diameter of the hub structure, and to these ends to make the pitch adjusting mechanism more compact, while also rendering it readily accessible.

With this purpose in view the invention contemplates utilizing the trunnion within the blade root for other functions than it has hitherto served; and a principal part of it lconsists in modifying the construction of the trunnion to enable it to perform these additional functions, and in modifications of the rest of the structure which are thereby rendered necessary and possible.

In particular the invention designs to employ the trunnion for holding the sliding pitch adjusting sleeve against rotation, and thereby relieving the hub structure of this function. A more important step is to transfer to the trunnion the function of transmitting driving torque to the propeller blade and of withstanding centrifugal forces. s This involves considerable strengthening and enlargementv of the trunnion, but as there is space for this within the propeller root no-increase in the total bulk of the structure is involved; on the contrary the hub structure can now be reduced in size and simplifiedso that a saving of weight is achieved and the overhang of the propeller is reduced.

It will be understood that by trunnion is here meant a radial projection from the propeller axis of circular cross-section and of robust oo construction appropriate to its functions; in the common case of a propeller with two blades the analogy with the trunnions of a gun is obvious.

Further features of the invention will appear from the following description of constructions embodying it which are illustrated in the accompanying drawings.

In these drawings,

Figure 1 is a part section and part end elevation of the centre of a propeller showing the 7o mounting of the blade and the provision for adjusting its pitch;

VFigure 2 is a section on the line lI-II of Figure 1;

Figure 3 is a halt axial section through an 75 alternative construction, and

Figure 4 is a part transverse section of it;

Figure 5 is a diagrammatic axial section through the shaft only illustrating a modified means of actuating the pitchadjusting mechaso msm.

In Figures 1 and 2 the trunnions 1 are cylindrical or tapered radial projections from a sleeve 2 integral with them and splined to the propeller shaft. 'I'he sliding pitch adjusting sleeve 3 is 55 splined upon this trunnion. It is equipped with both steep and shallow screw threads 4 and 5 respectively. These are shown as both external threads, this arrangement being most economical of space and Weight. With the steep pitch thread 4 there engages a correspondingly threaded member 6 forming part of or attached to a blade root mounting 7. This mounting has a conical skirt 8 upon which the root 9 of the propeller blade is seated and keyed; if preferred, however, the scating may be upon a cylindrical surface. The blade root is secured on the blade root mounting by the flanged ring 10 engaging the sleeve and screwing upon' the blade root.

A thrust and journal bearing shown as a ball 10o bearing 11 is interposed between the blade root mounting '7 and the trunnion 1 near their outer ends. One race 12 of the bearing rests upon a shoulder on the blade root sleeve while the other 13 is retained by a collar 14 screwing uponthe 105 trunnion. The races may be concentric and deeply recessed so that the bearing can take thrust in shear; but in the construction illustrated the one race is radially beyond the other s0 that the bearing takes centrifugal forces in 110 compression. A short cylinder 15 serving as a distance piece rests upon the race 12, surrounds the race 13 and forms an abutment for a locating washer 16 which extends over the race 13 and is pressed on the distance piece 15 by a ring 17 screwing into the endof the blade root sleeve. A similar ring 18 secures a protecting cap 19.

With the shallow pitch tnread upon the sliding sleeve 3 there engages a similarly threaded rotary pitch adjusting sleeve 20, carried in ball and roller bearings 21 in the blade root sleeve. The rotary sleeve 20 extends inward beyond the sliding sleeve 3 and a roller or other bearing 22 is interposed between it and the trunnion to complete the journal guidance of the blade. On the lower edge of the rotary sleeve 20 are bevel teeth 23.

The rotary pitch adjusting sleeves 20 are shown as operated through the medium of bevel segments 24 mounted on stud shafts 25 projecting from the sleeve 2 at right angles to the trunnions. These segments may be turned by any convenient means. The drawings show them equipped with spur teeth 26 with which engage racks 27 mounted to slide parallel with the propeller shaft in a casing member 28 embracing the shaft and the roots of the blades. These racks, together with dummy sliding rods 29, support a grooved ring 30 engaged by a control fork 31 in well known manner.

When it is desired to vary the pitch of the propeller blades the grooved ring 30 is shifted one way or the other by means of the control fork 31; the racks 27 engaging spur teeth 26 -turn the bevel segments 24 and through them the rotary sleeves 20. Since the ball bearing 21 prevents sleeve 20 moving endwise, and since the sleeve is screwed upon the shallow thread 5 of the sliding pitchadjusting sleeve 3 which is prevented from turning by its splined engagement with the trunnion 1, rotation of the sleeves 20 causes the sliding sleeves 3 to move inward or outward as the case may be. But the steep pitch thread 4 of each sleeve 3 engages the correspondingly Ithreaded member 6 upon the blade root sleeve 7; hence inward or outward movement of the non-rotating sleeves 3 causes the members 6 and therefore the blades to turn. This pitch-adjusting mechanism is selflocking, for torque upon the blades communicated to the members 6 cannot turn the sleeves 3 since they are splined upon the trunnion 1; nor can it shift the sleevesinward or outward both because the threads 4 are steep and because the threads 5 are shallow.

'I'he modified construction shown in Figures 3 and 4 differs from that just described chiefly in the fact that the thrust bearing 32 interposed between the blade root and the trunnion 1 is at the base of the trunnion. This makes possible some saving of weight in the outer part of the trunnion. A consequence of this change is that the rotary pitch adjusting sleeve 20 is now radially y and between the member 34 and the blade root sleeve to complete the journal guidance of the latter. The guidance of the rotary sleeve 20 is completed by the bearing 36. The spindle 33 has bevel'teeth 37 at its lower end, engaging a bevel pinon 38 supported within the sleev@ 2.- This pinion is turned by pinions 39 actuated through rack 27 and spur teeth 26.

The actuating mechanism here illustrated further difers from that previously described in that it is carried through the propeller shaft. A rod or tube 40 extending through the shaft may be moved longitudinally by the non-rotating part of the actuatingfmechanism (e. g. a lever replacing fork 3l), and communicates this movement to a shell 41 rotatably supported on it. An arm 42 upon the shell 41 is joined by 43 to the rack 27. In Figure 3, arm 42 and connector 43 have been turned out of their proper position into the plane of the section to show their structure.

The pitch adjusting mechanism may be controlled by hand or automatically, for instance by connection to a centrifugal governor driven by the engine. In either case the connection between the control handle or device and the pitchadjusting mechanism may be mechanical, as in the cases above described, or hydraulic. An example of a hydraulic connection between the nonrotating and rotating parts of the actuating mechanism is illustrated diagrammatically in Figure 5. A part of thel hollow propeller shaft 44 100 is utilized as a cylinder 45 for a piston 46 the piston rod 47 of which replaces the member 40 of Figure 3. It is shown as joined by a link directly to the bevel segments 24; ring conduits 49 and pipes 50 convey the fluid by which the device is operated.

It is claimed:

1. In a variable pitch propeller the combination of a propeller shaft, blades rotatably mounted thereon, a trunnion for each blade entering 1, the blade root and driven by the propeller shaft,

a sleeve slidable radially upon said trunnion and prevented from rotation thereon having both steep and shallow screw threads, a steep threaded member on the blade root engaged with said steep 1 15 tion of a propeller shaft, blades, a trunnion for 1,30

each blade capable of driving the blade, said trunnion being driven by the propeller shaft and entering the blade root, means for transmitting the radial stress on the'blade to the trunnion and for affording the blade journal support from .12,5

the trunnion at points a substantial distance apart, a sleeve with both steep and shallow threads slidable but not rotatable upon said trunnion its steep thread engaging a corresponding thread upon the blade root, a rotatable sleeve .18.0

held against axial movement having a shallow thread engaging the shallow thread of the slidable sleeve, and means for turning said rotatable sleeve.

3. In a variable pitch propeller the combina- 185 tion of a propeller shaft, blades, a trunnion for each blade capable of driving the blade, said trunnion being driven by the propeller shaft and entering the blade root, a thrust bearing interposed between the blade root and the'trunnion at the inner end of the trunnion to transmit to the trunnion the radial stress on the blade, a journal bearing between the blade root and trunnion at the outer end of the trunnion, a sleeve with both steep and shallow threads slidable but not rotatable upon said trunnion its steep thread engaging a corresponding thread upon the blade root, a rotatable sleeve held against axial movement having a shallow thread engaging the shallow thread 1 Y ofthe slidable sleeve, and means for turning said rotatable sleeve.

4. In a variable pitch propeller the combination of a propeller shaft, blades rotatably mountedrthereon, a trunnion for each blade entering the blade root and driven by the propeller shaft, a sleeve slidable radially upon said trunnion and prevented from rotation thereon having both steep and shallow screw threads on its outer surface, a steep threaded member on the blade root lengaged with said steep thread, a shallow threada radially sliding non-rotatable sleeve for each blade having both steep and shallow screw threads, a threaded member on the blade root engaging the steep thread of said sliding sleeve, a rotatable sleeve held against radial movement having a shallow thread engaging the shallow thread of said sliding sleeve, and means including a member passing through the hollow propeller shaft for turning said rotatable sleeve.

6. In a variable pitch propeller the combination of a propeller shaft, blades, a hollow trunnion for each blade capable of driving the blade, said trunnion being driven by the propeller shaft and entering the blade root, a thrust bearing interposed between the blade root and the trunnion at the inner end of the trunnion to transmit to the trunnion the radial stress on the blade, a

journal bearing between blade root and trunnion at the outer end. of the trunnion, a sleeve with both steep and shallow threads slidable but not rotatable upon said trunnion its steep thread engaging a corresponding thread upon the blade root, a rotatable sleeve held against axial movement having a shallow thread engaging the shallow thread of the slidable sleeve, a spindle fastened to said rotatable sleeve extending through the trunnion, and means for turning said spindle.

7. In a variable pitch propeller the combination of a hollow propeller shaft, blades, a trunnion for each blade capable of driving the blade, said trunnion being driven by the propeller shaft and entering the blade root, means for transmitting the radial stress on the blade to the trunnion and for affording the blade journal support from the trunnion at points a substantial distance apart, a sleeve with both steep and shallow threads slidable but not rotatable upon said trunnion its steep thread engaging a corresponding thread upon the blade root, a rotatable sleeve held AMELIA ANN LANZERO'ITI-SPINA, Executri of the Estate of Ettore Lanzerotti' Spina, Deceased. 

